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— _____. A. Twice a day B. Second C. Two D. Two times C 單元語法專練 ( )3. If my friends have any problems, my door is _____ open to them. A. never B. seldom C. sometimes D. always ( )4. Walking exercise is _____ boring at times but it’s fun to walk early on a sunny morning. A. may be B. never C. almost D. maybe D 單元語法專練 D ( )5. — __